FI65277C - ADJUSTMENT OF CHARGING FOR MODIFICATIONS OF MODIFIED EQUIPMENT - Google Patents

Description

ΓΒ1 ^ advertisement publication, r0nn ÄTa lBJ (11) UTLÄCGNINGSSKRIFT 65Z // C (45) ra le. · ‘Y 10.4 1:34

Patent meddelat V * (51) ttr.i ^ Wct. 3 c 13 L 1/08, G 08 B 31/00 FINLAND —FINLAND (21) P «** nttU *» k * inu «- PKantaraBknlng 783530 (22) Hlkamlspiivt - Araeknlnpdag 20.11.78 (23) Allaipilvl — Gilcighecsdig 20.11 .78 (41) Tullut lulkhukil - Bllvtt offantllg 22.05.79

Pmtmttl. and rricitUrihallitu · (44) NWltMWpwonpvm.-, 0 ', * βλ

Patent-och reglutentyral — n '7 Arnokin uttagd och utijtirtften puMmrad ou.xc.uj (32) (33) (31) Fyydutty «Tuoikws — Bagtrd priorttac 21.11.77

France-France (FR) 773 ^ 930 (71) CPC Internetional Inc., International Plaza, Englewood Cliffs,

New Jersey 07632, USA (72) Pierre Hector Ernest Fostier, Lille, France-France (FR) (7 * +) Oy Kolster Ab (5I +) Method and apparatus for the preparation of modified starches -For refining and analysis of modified starches

The invention relates to a process for the preparation of modified starches and to an apparatus for carrying out the process.

Known methods for preparing modified starches comprise the steps of treating starch milk with various chemical reactants depending on the desired modification and purifying the treated suspension in hydrocyclones and drying in a centrifuge before passing the wet product to a pneumatic dryer.

The main disadvantage of this type of method is that it can cause very severe pollution in the waters into which the effluent is discharged. Such contamination is due in particular to the soluble substances present in such effluents, which include: - soluble substances in the starch milk used as a starting material.

2 65277 - soluble substances extracted in hydrocyclones during purification, and - soluble substances which pass into the centrifuged filtrate.

Soluble substances include decomposed starch, inactive components of reactants, salts formed in neutralization, etc. Until now, all wastewater has been discharged into the environment, thus polluting the surrounding water bodies. On the other hand, the treatment of waste water before its disposal is a very costly operation.

With the method of the present invention, the removal of contaminated water at the end of the process can be avoided. In the following, reference is made to the accompanying figure.

The invention relates to a process for the preparation of modified starches, wherein the starch in the form of starch milk is modified with chemical reactants in the reaction chamber 9 and the modified starch is centrifugally dried in a centrifuge 10. The process is characterized by , wherein the filtrate from the centrifuge 10 in its entirety is returned for use as at least a portion of the dilution water.

Starch means all commonly used starches, such as corn, wheat or rice starch, and potato, tapioca or other powders.

In the process using starch milk as a starting material, a first drying step is performed before the reaction chamber, followed by a dilution step, a second drying step after the reaction chamber, and the filtrate from the second drying step is used as process water, which is returned at least once to the dilution step.

The removal of contaminated water is thus avoided by returning the effluent loaded with solutes to process water. As a result, some of the solutes are again included in the dried final product while the other part remains in the recycle water. The proportion of soluble residues in the obtained modified starch tends towards the limit which is practically reached after a few cycles, as will be explained in more detail below.

The degree of dilution of the substances contained in the circulating water can be freely adjusted by adding fresh water, preferably to the filtrate obtained from the second drying step. The reactants required for the preparation of the modified starch are added before the reaction chamber 9 with stirring and possibly heating with the filtrate from the drying step carried out in the centrifuge 10.

The invention also relates to an apparatus for carrying out the method. The apparatus according to the invention is characterized in that it comprises a first centrifugal dryer 2 connected to a feeder for feeding starch milk and having a cake remover connected to a dilution tank 5 arranged in series with a mixer 7 with devices for feeding reactants and optionally a heater 8 extending into a reaction chamber 9 with suitable supply lines and a discharge device connected to a second, modified starch centrifugal dryer 10, the filtrate discharge devices 11, 12 being connected to a line 18 for supplying dilution water to the dilution tank.

The filtrate removal device of the centrifugal dryer 10 may be provided with a device 13 for concentrating the insoluble substances contained in the filtrate, whereby such substances can be returned to the centrifugal dryer 10.

A safety filter 14 can be connected to the return line of the filtrate from the centrifugal dryer 10 downstream of the concentrator 13. The mixer is preferably of the static type and the fresh water supply device can be placed at the inlet end of the safety filter.

In the following, the attached figure, the apparatus and the steps of the method according to the invention are examined in more detail.

The figure shows the inlet 1 of starch milk, which, as is well known, comes as such from starch milk production plant A (not shown) to the first centrifugal dryer 2. The filtrate from the dryer is conveyed via line 3 to starch milk production plant A, which feeds starch milk. The dried cake, which contains about 35% moisture, is conveyed, e.g. by means of a screw and a conveyor belt 4, to a dilution tank 5 equipped with a suitable mixer and redispersed in the water fed from the inlet 6 to reconstitute the starch milk.

All the equipment used in the process is arranged in series. Thus, the outlet from the dilution tank 5 is connected to a mixer 4 65277, for example of the static type, and possibly connected to a heater 8 extending into a reaction chamber, i.e. a tank 9, which in turn is connected to a second centrifugal dryer 10 with a filtrate outlet 11 wherein the process water is optionally returned via a concentrator 13 and a safety filter 14, the fresh water inlet 15 being arranged at the inlet point of the filter.

The mixer 7 has, as usual, an inlet 16 for a suitable reactant, an inlet 17 for an alkali, catalyst or other substance and an inlet for water 18. The reaction vessel 9 has an inlet 19 for an acidic or neutralizing agent. The second dryer 10 comprises an outlet device 20 for the modified starch-forming cake and the outlet device 20 is connected, for example, to a suitable dryer S. The filtrate outlet device 11 may be connected to a concentrator 13 from which the filtrate is returned to the centrifugal dryer 10 via an inlet 22. In addition, for practical reasons, an exchange tank 23 can be placed between the dilution tank 5 and the mixer 7. The water used to redisperse the cake from the centrifugal dryer 2 in the dilution tank 5 consists mainly of the filtrate from the centrifugal dryer 10. The density of the starch milk is freely adjustable, but is preferably dj ^ = 1.184 to 1.188.

The feed of starch milk towards the reaction tank 9 is carried out at a rate which depends on the capacity of the circulation process and the reaction time. Preferably, the speed is selected so as to allow the dryer S to operate continuously. During the pumping, the starch milk fed to the reaction tank 9 circulates through one or more static mixers 7, whereby starch modifiers such as liquefiers, compounds which together with starch form substituted products, catalysts, or starch-improving products can be added through the inlets 16 and 17. swelling, especially at high pH values and temperatures. The starch milk then flows through a heater 8, which is usually a plate-type heat exchanger with sufficient capacity to convey the starch milk at the designed maximum production rate, usually at a temperature of 40-55 ° C.

The reaction starts at the outlet of the heating device 8. Neutra- I; The warping agent which terminates it, which may be an acid or a base, is fed directly to the reaction vessel 9 via inlet 19.

The reaction tank 9 has a capacity equal to that of the tanks 5 and 23, and the time required to empty it depends on the capacity of the centrifugal dryer 10 and the dryer S, which is usually of the pneumatic type.

The filtrate from the centrifugal dryer 10 is usually loaded with insoluble starch. This starch can be separated by taking advantage of its different density by passing it through at least one concentrator 13, which may be, for example, of the hydrocyclone type. The concentrated insoluble starch fraction is then returned via line 21 to the centrifuge feed 10 and the clarified fraction obtained via line 24 is used as described above for diluting starch in tank 5 and for diluting chemical reactants and additives (at 18). The safety filter 14 removes any remaining non-dissolved starch.

In practice, it is sufficient for the process to use two reaction vessels to ensure continuous production. All containers are preferably of similar capacity and are equipped with mixing devices.

It has been found that the proportion of soluble substances remaining in the modified starch produced in the process according to the invention tends, during successive reactions, towards the limit practically reached after five or six cycles, corresponding to the amount of dissolved starch and added or single reactants .

The following is a simplified system defined by the following weights: - total solutes formed or added during one reaction cycle = x, - dry feedstock = 100, - water from centrifuged starch feedstock = 59, - circulating water = V = 91, - water total * Vo = 150, - modified starch = 100, - modified starch water = 59.

65277

Since the distribution of solutes in the aqueous phase is constant, it is possible to calculate the increases in their concentration during successive cycles:

Weight of solutes in circulating water:

Reaction 1 X x V_ = "X x V_

Vo Vo

Reaction 2 (X x V_ +%) V_ =% x V_ (1+ V)

Vo Vo Vo Vo

Reaction 3 X x V_ (1 + ν _). + · Χ V_ = X x V_ 1 + V_ +, V. 2

Vo Vo J Vo Vo Vo 1Vo '

Reaction n »XxVl + V.fV.2 v3 L vö w · *

When V_ <1, which is valid in this method, and when Vo is an infinite number of reaction cycles, n is the series value of solutes in circulation X x V_ multiplied by the ratio V_ of the geometric series sum-Vo Vo racket as follows: circulating solutes _ __

Ra jamas = TL. x V x 1 = Xv

Vo 1 - V Vo - V

Vo _

Proportion of soluble substances in circulating water = TC x 100 water

Vo - V * of which = 1.69 X% / water in this example.

Content of soluble substances in starch = X x 100 Vo - V = X% /

Vo - V X 100 dry matter.

Thus, the calculation gives a logical result, because the amount of substances added in such an isolated system must correspond to the amount of substances coming from it.

The chemical additives used in the reaction are in some cases not found in the liquid phase because they are present, at the end of the process, in a form that is insoluble or sparingly soluble in water (such as calcium sulfate obtained by neutralizing sulfuric acid with lime or calcium carbonate). The proportion of foreign substances in the 7 65277 finished starch then reaches its limit faster, but the limit remains the same and the circulating liquids are less loaded with solutes.

In cases where circulating fluids have to be stored for a rather long production downtime, it is desirable to protect them from the risk of fermentation during storage. Certain preservatives, such as sodium hypochlorite, have been shown to be effective for this purpose when used in small amounts.

The following examples illustrate the invention.

Example 1

Preparation of liquefied starch by the acid process This process is carried out in a similar manner to that described above, using four tanks of equal capacity, namely one tank for dispersing centrifuged starch, one exchange tank and two reaction tanks.

Hydrochloric acid (d = 1.16) is used for liquefaction in a ratio of 40 l / ton of starch-dry matter.

Hydrochloric acid is continuously fed to the starch milk during the filling of the reaction tank for three hours via a static mixer. A plate-type heater located immediately downstream raises the temperature of the starch to 52-53 ° C.

At the end of the reaction, neutralization is carried out with sodium carbonate powder and the pH is adjusted to 6.

Since the capacity of the process is such that the reaction tank must be emptied in 11 hours, the time available for the liquefaction reaction (11 h - 3 h) = 8 h + half the tank filling time, as the starch begins to change immediately after leaving the heater, namely 1 hour and 30 hours. after 1 minute, i.e. a total of 9 h 30 min. This time is sufficient to achieve the desired viscosity reduction, with 13 end cycles of the end product of each reaction cycle having a Scott viscosity (60 g of starch - 100 ml pour) of 45-60.

Continuous operation with two reaction vessels is programmed according to the following Table I, in which numerical values are expressed in hours.

8 65277

Table I

Reaction tanks No. 1 No. 2 No. 1 No. 2 Starch dispersion begins Oh 11 h 22 h 9h Starch dispersion ends 4 15 2 13 Exchange tank full 5 16 3 14 Reaction tank full 8 19 6 17 reaction completed 16 3 14 1 reaction vessel empty 3 14 1 12

There are no interruptions in the feed downstream of the reaction tank.

For practical reasons and to allow a certain delay in the recovery of the filtered water used to disperse the starch, 400 l of additional water per tonne of starch-dry matter are added during the first dispersing step.

The first two steps are performed with starch milk (d ^ = 1.184), which comes directly from the starch plant, without centrifugation.

From the third stage onwards, the cycles become normal. The accumulation of soluble residues in the produced liquefied starch is shown in the following Table II:

Table II

Soluble substances in the final product (% dry matter)

Inorganic Organic Total 1st cycle 0.95 0.40 1.35 2nd cycle 1.50 0.65 2.15 3rd cycle 1.85 0.80 2.65 4th cycle 2.10 0.90 3, 00 5th cycle 2.20 0.95 3.15 6th cycle 2.30 0.95 3.25 7th cycle 2.35 1.00 3.35 limit 2.40 1.00 3.40

The limit value for soluble substances is reached at about the sixth cycle. The dry matter content of all solubles after mixing in the different reaction cycles is on average 2.70%.

li 65277

Example 2

Preparation of Cationic Starch This process is carried out with the equipment used in the preparation of the liquefied starch described in Example 1.

The reactant used is a quaternary ammonium compound which is an epoxy reagent (2,3-epoxypropyltrimethylammonium chloride). It is added to the starch milk in 20 parts per 1000 parts of starch-dry matter during the pumping of the starch, and a static mixer is used for the addition.

The reaction catalyst, which is sodium hydroxide, is then added in a ratio of 12 parts per 1000 parts of dry starch. The base is first dissolved and then diluted in 120 l of water similar to the water used to disperse the starch, after which it is continuously and evenly injected into the starch milk via a second static mixer. Since the dilution water of the base must be free of insoluble starch, a safety filter was used which retained particles larger than 3 microns to complete the concentration and clarification of the liquids coming from the centrifuge.

The starch milk is heated to a reaction temperature of 49 ° C by passing it through a plate-type heat exchanger.

It takes 3 hours to fill the reaction tank, and with this two-tank system, the time required for the reaction and its completion is therefore 9 hours 30 minutes, with the required reaction time being 8 hours. When the conversion is complete, the starch is neutralized with hydrochloric acid (d = 1.16), which has a pH close to 5.0.

The first two steps did not need to be performed with non-lingo-starched milk and did not require the use of extra water for the first dispersion of the centrifuged starch, as the remaining filtered water stored after the preparation of the liquefied starch of Example 1 was used. to disperse the starch.

After 14 reaction cycles, the modified starch finally produced has the following characteristics: moisture: 12% pH: 5 degree of substitution: 0.017 10 6 52 77 total solutes: less than 2.5% inorganic matter: less than 1.75%.

The accumulation of soluble residues in the cationic starch prepared in this way is shown in Table III below (in which case it should be noted that one cycle corresponds to two reaction cycles).

Table III

Soluble substances in the final product (% dry matter)

Inorganic Organic Total 1st cycle 1.49 0.83 2.32 2nd cycle 1.60 0.79 2.39 3rd cycle 1.66 0.78 2.44 4th cycle 1.69 0.77 2, 46 Cycle 5 1.71 0.76 2.47 Cycle 6 1.73 0.75 2.48 Cycle 7 1.73 0.75 2.48 Limit 1.73 0.75 2.50 This example shows that it is possible to reuse liquids remaining after the production of a certain modified starch for the production of another type of modified starch, provided that these liquids are stored in such a way that they are protected from fermentation (in this example 1 l of hypochlorite with a concentration of 155 g of active starch was added). chlorine / l, per cubic meter of water) and provided that the manufacturing processes for the different modified starches are programmed in such a way as to avoid incompatibilities.

The soluble compounds caused by liquefied starch present in the circulating water decrease from one cycle to another in a geometric series, finally approaching the zero limit. The limit of soluble substances which is finally achieved in the manufacture of cationic starch thus does not differ from the limit which would be obtained by using pure water.

Example 3

Manufacture of oxidised starch

The process is carried out as described above, using 4 tanks comprising starch dispersing, L1 X1 65277 exchange and reaction tanks, and equipment for injecting the reactant during pumping into the reaction tanks.

The reagent used is a solution of sodium hypochlorite with a titration of 150 g C / l and containing 48 g / l sodium.

Using a static mixer, the reactant is injected into the starch milk throughout the reaction tank. requires to be met. A plate-type heater located immediately downstream raises the temperature to approx. 40 ° C if necessary.

The amount of hypochlorite solution injected is such that the ratio of added chlorine to dry starch is about 1.2. The reaction time is about 3 hours.

The oxidized starch produced has the following characteristics: moisture: 12% pH: 8-9 carboxyl groups: 0.1% total solubles 3.8% inorganic solutes: 2.8%

The percentage of soluble residues in oxidized starch is shown in Table IV below.

Table IV

Soluble substances in the final product (% dry matter) • Inorganic Organic Total 1st cycle 1.07 0.39 1.46 2nd cycle 1.72 0.62 2.34 3rd cycle 2.12 0.77 2.89 4 cycle 2.37 0.86 3.23 5th cycle 2.50 0.91 3.41 6th cycle 2.60 0.94 3.54 7th cycle 2.65 0.96 3.61 limit 2, 70 1 3.70

Example 4

Manufacture of acetylated starch

The process is carried out as described in Example 1. 4 tanks of similar capacity are used, comprising: 12 65277 one tank for dispersing centrifuged starch, one exchange tank and two reaction tanks.

The reactant used is acetic anhydride and the catalyst is a sodium carbonate solution prepared in advance by dissolving the flaked sodium carbonate in a suitable amount of water taken from the cycle. The two solutions are evenly injected into the starch milk by pumping it into the reaction tank until the amounts of 3000/1000 and 19/1000, respectively, are reached.

Since the sodium carbonate dilution water must be free of insoluble starch, a safety filter with a retention size of 3 microns is used, as in Example 2 above.

The acetylated starch produced has the following characteristics: moisture: 12% pH: 5-6% acetyl% soluble solids: less than 4.2% inorganic solutes: less than 3.7%.

The percentage of soluble residues in the modified starch is shown in Table V below.

Table V

Soluble substances in the final product (% dry matter)

Inorganic Organic Total 1st cycle 1.33 0.20 1.53 2nd cycle 2.18 0.30 2.48 3rd cycle 2.74 0.35 3.09 4th cycle 3.07 0.40 3, 47 5th cycle 3.30 0.45 3.75 6th cycle 3.45 0.45 3.85 7th cycle 3.53 0.48 4.01 limit 3.70 0.50 4.20 13 65277

The process can be carried out to prepare acetylated starch, using water recovered during the preparation of oxidized starch (see previous example) to resuspend the starch.

Under these operating conditions, the same characteristics are obtained as above, although the results obtained by analyzing the starches from the different reaction cycles are more uniform.

The percentage of soluble residues in starch is shown in Table VI below.

Table VI

Soluble substances in the final product (% dry matter)

Inorganic Organic Total 1st cycle 3.69 1.04 4.73 2nd cycle 3.69 0.84 4.53 3rd cycle 3.71 0.65 4.36 4th cycle 3.69 0.62 4, 31 Cycle 5 3.69 0.59 4.28 Cycle 6 3.70 0.54 4.24 Cycle 7 3.69 0.54 4.23 Limit 3.70 0.55 4.25 Variation of this invention According to the invention, it is possible to start with comminuted starch with a moisture content of about 12% and place it as a suspension directly in the dilution tank, the first centrifugal drying step being carried out before such starch is dried.

The method of this invention is useful for any starch modification that does not result in grain degradation. The solutes containing the final product may optionally contain a small amount of degraded starch, unreacted components of the reactants, and salts from neutralization or other chemical additives. The modified starches obtained by the process of this invention are in particular: - starches liquefied in an acidic or oxidizing medium, - starches crosslinked with multifunctional groups, 14 65277 - cationic starches, - starch starches, - acetylated starches, - carboxymethyls, in the medium, - phosphatized starches.

The modified starches obtained according to the invention can be used in particular for the preparation of starch pastes.

Claims (10)

A process for preparing modified starches, wherein starch milk starch is modified with chemical reactants in a reaction chamber (9) and the modified starch is rotated in a centrifuge (10), characterized in that starch milk, which from the starch's preparation step to the modification step, a first drying in a centrifuge (2) and the cake obtained from the centrifuge (2) are diluted for the modification, the filtrate obtained from the centrifuge (10) being fully returned for use as at least some of the dilution water. Process according to Claim 1, characterized in that the degree of dilution of the substances contained in the circulation water is freely controlled by adding fresh water, preferably to the filtrate obtained from the second rotary drying step carried out in the centrifuge (10). 3. A process according to claim 1 or 2, characterized in that the rotary dried cake obtained from the second rotary drying step, which forms the modified starch, is dried. 4. An installation for carrying out the method according to any preceding claim, characterized in that it comprises a first rotary dryer (2), which is connected to a starch milk feeding device and whose outlet device for the cake is connected to a dilution tank (5). arranged in series with a mixer (7) having feeder means for the reacting agents, and optionally with a heater (8), which opens into a reaction chamber (9) with suitable feeder lines and with its outlet device coupled to a second modified starch rotary dryer (10), wherein the filtrate outlet means (11, 12) are connected to the dilution water line (18) for the dilution tank. 5. An installation according to claim 4, characterized in that the apparatus for removing the filtrate from the second rotary dryer (10) comprises a concentrator (13) for insoluble substances contained in the filter, which concentrator is arranged to return these substances to the other rotary torque (10). Installation according to claim 4 or 5, characterized in that a safety filter (14) is connected to the pipe,